<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        * {
            padding: 0;
            margin: 0;
        }
        .left {
            margin-right: 250px;
            height: 600px;
            background-color: lightcoral;
        }
        .right {
            position: absolute;
            right: 0;
            height: 600px;
            width: 250px;
            background-color: lightblue;
            /* opacity: 0.5; */
        }
    </style>
</head>
<body>
    <!-- 左边宽度自适应，右边固定 -->
    <div class="right">推荐信息</div>
    <div class="left">主体内容</div>
</body>
</html>